1. Field of the Invention
The present invention relates generally to tape cassette reels and more particularly to a tape cassette reel having an upper reel portion formed by a dichromatic molding method.
2. Description of the Prior Art
FIG. 1 shows an example of a prior-art tape cassette for use with a so-called 8 mm video tape recorder.
Referring to FIG. 1, it will be seen that a cassette body 1 is comprised of an upper cassette half 2a, a lower cassette half 2b and a tape protecting member 3. The upper cassette half 2a and the lower cassette half 2b are coupled to each other to form a box. The tape protecting member 3 is rotatably attached to the box portion. A transparent, rectangular window 4 is formed on the upper surface of the upper cassette half 2a. Supply and take-up or cassette reels 5S and 5T are provided within the cassette body 1 so as to become freely rotatable. A tape 6 is wound around the cassette reels 5S and 5T through the tape protecting member 3, while both ends of the tape 6 are respectively fixed to the cassette reels 5S and 5T.
Cassette reel pushing springs 7, 7 are provided on the upper surface of the cassette body 1. The cassette reel pushing springs 7, 7 are respectively engaged with center pins 9 (FIG. 2) provided at the central, upper end portion of each of the cassette reels 5S and 5T, as will be described later. Further, a braking member (not shown) is also provided within the cassette body 1 so as to mesh with a brake engaging tooth 12 (FIG. 2) formed around the lower reel portion of each of the cassette reels.
According to the above-mentioned cassette body, it is possible to visually confirm the wound condition of the tape 6 around the cassette reels 5S and 5T through the transparent, plastic window 4 formed on the upper cassette half 2a. If the upper reel or flange portion of each of the cassette reels 5S, 5T is completely made of a transparent, resin material, the inside structure of the reel hub is seen from the outside. To solve this problem, the assignee of the present application has previously proposed a tape cassette reel in which a central portion 15 of an upper flange portion of each of the cassette reels 5S, 5T is formed by a desired opaque material and a peripheral portion 14 of the upper flange portion is formed of a transparent material by a dichromatic molding method. This previously-proposed tape cassette reel will be described hereinunder with reference to FIGS. 2 to 4.
FIG. 2 is a perspective view illustrating an overall arrangement of each of the tape cassette reels 5S, 5T, FIG. 3 is a side view of a section of a reel hub portion of each of the tape cassette reels 5S, 5T shown in FIG. 1 and FIG. 4 is a plan view of each of the tape cassette reels 5S, 5T.
Referring to FIGS. 2 to 4, it will be seen that the tape cassette reels 5S, 5T is comprised of a reel hub 10 formed as one body with a lower flange portion 8 and an upper flange portion 13 secured to the upper end face of the reel hub 10. The upper flange portion 13 is comprised of the peripheral portion 14 made of a transparent, synthetic resin and the central portion 15 made of a desired, opaque material. The upper flange portion 13 is provided with protruded portions 16, 16 formed on the lower end face at its central portion 15 which are fixed to upper end faces 17, 17 of the reel hub 10 by means of an ultrasonic welding-process. Further, a circular concave portion 18 is formed on the upper surface of the upper flange portion 13. An aperture 19 is formed through the central portion 15 of the upper flange portion 13, and a center pin 9 is loosely supported between the central, lower surface of the upper flange portion 13 and the central, upper end face of the reel hub 10. The center pin 9 forms a contact portion which comes in contact with the cassette reel pushing springs 7 provided in the cassette housing 1.
As shown in FIG. 3, a hub drive shaft engaging aperture 20 is formed on the lower surface side of the reel hub 10 so that it can be engaged with a hub drive shaft of an 8 mm video tape recorder body (not shown). As shown in FIG. 2, a clamp piece engaging portion 21 is formed around the peripheral surface of the reel hub 10. The clamp piece engaging portion 21 is used to fix the tape end thereto together with a clamp piece (not shown). Reel brake engaging teeth 12 are formed around the outer peripheral surface of the lower flange portion 8. In FIG. 2, reference numerals 22, 22 designate protruded portions which are used as pouring gates.
According to the above-mentioned prior-art tape cassette reel, when the upper flange portion 13 is formed by the dichromatic molding method, if the tape cassette reel is very small, just like a tape cassette reel for a tape cassette of 8 mm video tape recorder, then the thickness of the upper flange portion 13 is decreased and hence the bonding strength of resin on the bonding surface between the transparent peripheral portion 14 and the central portion 15 made of the colored resin is considerably decreased. The bonding surface can not obtain sufficient bonding strength because the peripheral portion 14 and the central portion 15 are molded from different synthetic resins and the molding conditions thereof are not equal.